Lipid measuring apparatus and lipid measuring method

ABSTRACT

An apparatus and a method that readily allow noninvasive lipid measurement with no skill of a measurer. The apparatus includes an irradiator that radiates light having a predetermined light intensity to a predetermined site of a living body from outside the living body toward inside the living body, a light intensity detector that detects a light arrival range in the living body based on the light intensity of light emitted from the living body, and a controller that calculates a predetermined light arrival range parameter based on the light arrival range and calculates lipid concentration in the living body based on the light arrival range parameter.

TECHNICAL FIELD

The present invention relates to a lipid measuring apparatus and a lipidmeasuring method.

BACKGROUND ART

Attention has been directed to postprandial hyperlipidemia as a riskfactor for arteriosclerosis. There has been a report stating that anincrease in the concentration of neutral lipid in a non-hunger stateincreases the risk of development of an event of coronary arterydiseases.

To diagnose postprandial hyperlipidemia, it is necessary to observe achange in in-blood lipid concentration for 6 to 8 hours after meals.That is, to measure the state of hyperlipemia, it is necessary to placea subject under restraint for 6 to 8 hours and collect blood multipletimes. The diagnosis of postprandial hyperlipidemia is therefore nobetter than clinical studies, and diagnosing postprandial hyperlipidemiaat a clinical site is not practical.

Patent Literature 1 discloses an approach to a solution of the problemdescribed above. According to the approach disclosed in PatentLiterature 1, noninvasive lipid measurement can eliminate bloodcollection. The in-blood lipid can therefore be measured not only in amedical institution but at home. Allowing instantaneous data acquisitionallows temporally continuous in-blood lipid measurement.

CITATION LIST Patent Literature

Patent Literature 1

International Publication No. 2014/087825

SUMMARY OF INVENTION Technical Problem

In the noninvasive lipid measuring approach shown in Patent Literature1, however, determination of an optimum measurement site requires skillof a measurer, causing a measurement error.

When light passes through a living body, the skin, muscle, blood, andother factors attenuate the intensity of the light. To detect theconcentration of a specific substance in a living body, it is desirableto minimize influences other than a target under measurement.

On the other hand, since the precision of measurement is expressed bythe ratio of a signal to noise (S/N), it can be said that themeasurement precision can be improved by detection of an increasedintensity of a signal from the target under measurement.

The measurement approach shown in Patent Literature 1, although it isbased on one-dimensional (linear) detection, has a difficulty inmeasurement at a single site due to positional displacement of ameasurement instrument, attachment and detachment of the measurementinstrument to and from a subject, and other factors during themeasurement because the light diffuses nonuniformly due, for example, tothe veins, muscles, and bones. Therefore, to perform precisemeasurement, the measurer requires skill.

The present invention has been made to solve the problems with therelated art, and an object of the present invention is to provide anapparatus and a method that readily allow noninvasive lipid measurementwith no skill of a measurer.

Solution to Problem

A lipid measuring apparatus according to the present invention includesan irradiator that radiates light having a predetermined light intensityto a predetermined site of a living body from outside the living bodytoward inside the living body, a light intensity detector that detects alight arrival range in the living body based on a light intensity oflight emitted from the living body, and a controller that calculates apredetermined light arrival range parameter based on the light arrivalrange and calculates lipid concentration in the living body based on thelight arrival range parameter.

A lipid measuring method according to the present invention includes anirradiation step of radiating light having a predetermined lightintensity to a predetermined site of a living body from outside theliving body toward inside the living body, a light intensity detectionstep of detecting a light arrival range in the living body based on alight intensity of light emitted from the living body, a parametercalculation step of calculating a predetermined light arrival rangeparameter based on the light arrival range, and a lipid concentrationcalculation step of calculating lipid concentration in the living bodybased on the light arrival range parameter.

A lipid measuring apparatus according to the present invention is alipid measuring apparatus communicably connected to a user apparatusincluding an irradiator that radiates light having a predetermined lightintensity to a predetermined site of a living body from outside theliving body toward inside the living body, a light intensity detectorthat detects a light arrival range in the living body based on a lightintensity of light emitted from the living body, and a communicationsection that transmits the light arrival range detected by the lightintensity detector, the lipid measuring apparatus including a controllerthat calculates a predetermined light arrival range parameter based onthe light arrival range transmitted from the user apparatus andcalculates lipid concentration in the living body based on the lightarrival range parameter.

Advantageous Effects of Invention

The lipid measuring apparatus and method according to the presentinvention readily allow noninvasive lipid measurement with no skill of ameasurer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the configuration of a lipid measuring apparatus accordingto an embodiment.

FIG. 2 shows that light is scattered by lipid in the blood.

FIG. 3 shows the configuration of a control system of the lipidmeasuring apparatus according to the embodiment.

FIG. 4 shows a light arrival range having a circular shape.

FIG. 5 shows the light arrival range having a distorted shape.

FIG. 6 is a flowchart of a method for operating the lipid measuringapparatus according to the embodiment.

FIG. 7 shows the configuration of a lipid measuring system according tothe embodiment.

FIG. 8 shows the configuration of a control system of a lipid measuringapparatus according to the embodiment.

FIG. 9 shows a result of imaging of the light arrival range.

FIG. 10 shows a result of imaging of the light arrival range.

FIG. 11 shows a result of imaging of the light arrival range in thevicinity of the veins.

FIG. 12A compares a change in lipid concentration and a change in thearea of the light arrival range.

FIG. 12B compares the change in lipid concentration and the change inthe area of the light arrival range.

FIG. 13A shows the relationship between a minimum light arrival distanceand the lipid concentration.

FIG. 13B shows the relationship between the minimum light arrivaldistance and the lipid concentration.

FIG. 14A shows the relationship between a light arrival volume and thelipid concentration.

FIG. 14B shows the relationship between the light arrival volume and thelipid concentration.

FIG. 15 shows the arrangement of an irradiator and a light intensitydetector that differs from the arrangement shown in FIG. 2.

FIG. 16 shows an example of the result of imaging based on thearrangement of the irradiator and the light intensity detector shown inFIG. 15.

FIG. 17A shows results of measurement based on the arrangement of theirradiator and the light intensity detector shown in FIG. 15.

FIG. 17B shows results of the measurement based on the arrangement ofthe irradiator and the light intensity detector shown in FIG. 15.

DESCRIPTION OF EMBODIMENT

A lipid measuring apparatus according to an embodiment of the presentinvention and a method for operating the same will be described below indetail with reference to the drawings.

FIG. 1 shows the configuration of the lipid measuring apparatusaccording to the embodiment.

A lipid measuring apparatus 100 according to the embodiment includes anirradiator 101, which radiates light to a predetermined site of a livingbody from outside the living body toward the interior of the livingbody, a light intensity detector 102, which receives light emitted fromthe living body and detects a light arrival range F in the living bodybased on the light intensity of the received light, and a controller103, which calculates a light arrival range parameter based on the lightarrival range F detected by the light intensity detector 102 andcalculates lipid concentration based on the light arrival rangeparameter, as shown in FIG. 1.

The irradiator 101 includes a light source for radiating the light to apredetermined irradiation position on the predetermined site of theliving body from outside the living body toward the interior of theliving body. The irradiator 101 in the embodiment can adjust thewavelength of the radiated light. The irradiator 101 can adjust therange of the wavelength in such a way that the wavelength range does notfall within the range of the wavelengths at which the light is absorbedby inorganic substances of the blood plasma. The irradiator 101 canperform the adjustment in such a way that the wavelength range does notfall within the range of the wavelengths at which the light is absorbedby the cell components of the blood. The cell components of the bloodare formed of the red blood cells, white blood cells, and platelets inthe blood. The inorganic substances of the blood plasma are formed ofwater and electrolytes in the blood.

The range of the wavelength of the light radiated by the irradiator 101is preferably formed of the range shorter than or equal to about 1400 nmand the range from about 1500 to 1860 nm in consideration of the rangeof the wavelengths at which the light is absorbed by the inorganicsubstances of the blood plasma. Further, the range of the wavelength ofthe light radiated by the irradiator 101 is more preferably formed ofthe range from about 580 to 1400 nm and the range from about 1500 to1860 nm in consideration of the range of the wavelengths at which thelight is absorbed by the cell components of the blood.

The thus set wavelength range used by the irradiator 101 suppresses theinfluence of the inorganic substances of the blood plasma on the lightabsorption and the influence of the cell components of the blood on thelight absorption of light to be detected by the light intensity detector102, which will be described later. In the thus set wavelength range, noabsorption large enough to identify a substance is present, wherebylight energy loss due to the absorption is negligibly small. The lightin the blood therefore propagates over a large distance when scatteredby lipid in the blood and exits out of the living body.

The irradiator 101 in the embodiment can arbitrarily adjust the timelength, for example, for which continuously light or pulsed light isradiated. The irradiator 101 can arbitrarily modulate the intensity orphase of the radiated light.

The irradiator 101 may be formed of a light source having a fixedwavelength. The irradiator 101 may instead be formed of the combinationof a plurality of light sources having different wavelengths or thecombination of light fluxes having a plurality of wavelengths.

The light intensity detector 102 receives light emitted out of theliving body, detects the light intensity of the light, and detects thelight arrival range F in the living body.

FIG. 2 shows the light scattered by lipid in the blood. The light (B inFIG. 2) radiated from the irradiator 101 to an irradiation position (Ein FIG. 2) on the surface of a living body D arrives at the depth wherelipid, such as lipoprotein, is present and is then reflected offin-blood lipid (A in FIG. 2) in the living body D, as shown in FIG. 2.Further, after the radiated light is scattered by the lipid in theblood, and resultant back-scattered light (C in FIG. 2) is emitted fromthe living body. The light intensity detector 102 detects the lightintensity of the back-scattered light C.

In FIG. 2, the front end of the irradiator 101 is in contact with theliving body D and may instead be separate from the living body D by apredetermined distance, as shown in FIG. 13.

The distance from the irradiation position E, to which the irradiator101 radiates light, to the outer circumference of the range over whichthe light intensity has a predetermined level (hereinafter referred toas light arrival range F) is called a light arrival distance l, as shownin FIG. 2.

Lipoprotein, which is the target under measurement, has a sphericalstructure covered with apoprotein and other substances. Lipoprotein ispresent in the form of a solid-like state in the blood. Lipoprotein ischaracterized in that it reflects light. In particular, chylomicron(CM), VLDL, and other substances having a large particle diameter andspecific gravity contain a large amount of triglyceride (TG) and arecharacterized in that they are more likely to scatter light. The lightintensity detected by the light intensity detector 102 is affected bythe light scatted by lipoprotein.

The light intensity detector 102 may be a CCD or CMOS element or anyother light receiving element. The light intensity detector 102 mayinstead be formed of light receiving elements arranged in an array or ina concentric form. To reduce the number of light receiving elements, thelight receiving elements may be arranged in the form of a cross or aletter V around the irradiation position E or may be linearly arrangedand moved or rotated in the measurement.

In FIG. 2, the light intensity detector 102 is placed immediately abovethe irradiator 101, but not necessarily, and may be located in anyposition where the light intensity detector 102 can detect the lightarrival range F.

The configuration of a control system of the lipid measuring apparatus100 will next be described. FIG. 3 is a block diagram of the lipidmeasuring apparatus 100 according to the embodiment. A CPU (centralprocessing unit) 104, a ROM (read only memory) 105, a RAM (random accessmemory) 106, a storage 107, an external I/F (interface) 108, theirradiator 102, and the light intensity detector 102 are connected toeach other via a system bus 109. The CPU 104, the ROM 105, and the RAM106 form the controller 103.

The ROM 105 stores in advance a program executed by the CPU 104 andthresholds used by the CPU 104.

The RAM 106 has an area where the program executed by the CPU 104 isdeveloped, a variety of memory areas, such as a work area where theprogram processes data, and other areas.

The storage 107 stores data prepared in advance on appropriate numericalranges of static and dynamic parameters. The storage 107 may be aninternal memory that stores information in a nonvolatile manner, such asan HDD (hard disk drive), a flash memory, and an SSD (solid-statedrive).

The external I/F 108 is an interface for communication with an externalapparatus, for example, a client terminal (PC). The external I/F 108only needs to be an interface that performs data communication with anexternal apparatus and may, for example, be an instrument (such as USBmemory) locally connected to the external apparatus or a networkinterface for communication via a network.

The controller 103 calculates the light arrival range parameter based onthe light arrival range F detected by the light intensity detector 102.

The light arrival range F may be detected by employing a binarizationmethod. The light intensity detected by the light intensity detector 102is divided into 256 segments from 0 to 255, and the light intensitydetector 102 sets a light intensity threshold at 254 so that 255 istaken as the light arrival range F.

The greater the distance between the irradiator 101 and the lightintensity detector 102 is, the better the detected light intensityreflects the influence of the scattering. The threshold is therefore notlimited to the value described above and may be lowered. In this case,the actual measurement is more likely to be affected by ambient light,and it is therefore preferable to timely set the threshold based on theshape of the apparatus, the degree of light blockage, and thesensitivity of the light receiving element.

In a case where the light receiver is formed, for example, of a PD, anAD value or a voltage value may be used as the threshold, and it ispreferable to appropriately set the measurement range used in themeasurement based on the intensity of the radiated light, thesensitivity of the light receiving elements, and the degree of lightblocking.

In the present example, in a case where the measurement is performed ina darkroom with the ambient light negligible, noise having a magnitudeof about 10 in terms of light intensity contaminates a result of themeasurement, measurement results having a light intensity of 11 andhigher have been examined.

FIG. 4 shows the light arrival range F on the surface of a living bodyviewed along the direction X in FIG. 2. In the case of capillaries only,the radiated light diffuses in the form of a circle having a radiusequal to the light arrival distance l around the irradiation position E,and the light arrival range F has a circular shape on the surface of theliving body.

The controller 103 calculates, as the light arrival range parameter, thedistance from the irradiation position E in the light arrival range F tothe outer circumference (outer edge) of the light arrival range (calledlight arrival distance l).

The controller 103 further calculates the area of the light arrivalrange F (called light arrival area S) as the light arrival rangeparameter. The light arrival area S may instead be calculated from thelight arrival distance l. The light arrival area S may still instead becalculated from the number of pixels having the threshold 255. Toaverage measurement errors, the light arrival area S may be calculatedin the form of the area of an ellipse having a maximum light arrivaldistance and a minimum light arrival distance as the major and minoraxes.

The controller 103 further calculates the volume of the light arrivalrange F (called light arrival volume V) as the light arrival rangeparameter. The light arrival volume V can be calculated by using thefollowing expression: V=(4/3π×a×b×c)/2.

The symbols a, b, and c in the expression are the radii of a sphere thatextend in directions x, y, and z of a coordinate system and intersectone another at right angles. In a case where the light arrival range isnot distorted, a=b=c is satisfied, whereby l=r in FIG. 2, and the lightarrival volume V is (4/3π×l³)/2).

The light arrival range parameter may therefore be any of the lightarrival area S, the light arrival distance l, the minimum light arrivaldistance l2, the light arrival area S and the minimum light arrivaldistance l2, the ratio or difference between the maximum light arrivaldistance l1 and the minimum light arrival distance l2, the light arrivalvolume V, the light arrival volume V and the minimum light arrivaldistance l2, or the combination thereof.

The controller 103 calculates the lipid concentration in the blood basedon the calculated light arrival range parameter (such as light arrivaldistance l and light arrival area S).

The area over which the radiated light diffuses decreases as the lipidconcentration in the blood changes. The reason for this can be inferredas follows: the distance over which the light diffuses decreases as thedegree of scattering of the light due to lipid particles in the bloodincreases. The lipid concentration calculator 104 therefore calculatesthe lipid concentration in the blood from the light arrival distance lor the light arrival area S. The approach described above does notdepend on the measurement site because the measurement can be made, forexample, only with information particularly on the capillaries.

The amount of change in lipid concentration and the light arrival area Sare so closely related each other that the correlation coefficient is0.875, as shown in FIG. 12B, whereby the lipid concentration can becalculated from a correlation coefficient specified in advance at leastwithin individual variation.

Instead, the controller 103 may calculate a scattering coefficient fromthe light arrival range parameter and then calculate the lipidconcentration. At a clinical site, the concentration and the turbidityare synonymous with each other in some cases, and the concentration inthe present invention includes the turbidity. The controller 103 cantherefore use not only the concentration but the number of particles perunit amount, the formazin turbidity, or the scattering coefficient as aresult of the calculation.

FIG. 5 shows the light arrival range F on the surface of the living bodyviewed along the direction X in FIG. 2. In a case where the light fromthe irradiator 101 passes though the veins, the light does not diffusein the form of concentric circles, and the light arrival range F has adistorted shape having the maximum light arrival distance l1 and theminimum light arrival distance l2 on the surface of the living body. Thecontroller 103 calculates the lipid concentration in the blood from theminimum light arrival distance l2. This approach is an approach thatallows the measurement in the case where the light passes through theveins.

The controller 103 may instead calculate the lipid concentration fromthe light arrival area S and the minimum light arrival distance l2.Information on the veins and capillaries as a whole can therefore beacquired even in a measurement site containing the veins.

The controller 103 may increase the precision of the measurement asinformation on the veins by calculating the ratio or difference betweenthe maximum light arrival distance l1 and the minimum light arrivaldistance l2. Further, the controller 103 may instead increase theprecision of the measurement as information on the veins by determiningthe ellipticity of the light arrival range F from the maximum lightarrival distance l1 and the minimum light arrival distance l2 ordetermining the area of the elliptic shape of the light arrival range F.

The lipid measuring apparatus 100 having the configuration describedabove performs lipid measurement based on a preset program. FIG. 6 is aflowchart of the lipid measurement according to the embodiment.

In an irradiation step (S101), the irradiator 101 radiates continuouslight to an irradiation position on a living body.

In a light intensity detection step (S102), the light intensity detector102 detects the light intensity of the light emitted from the livingbody around the irradiation position and detects the light arrival rangeF in the living body based on the light intensity. The light arrivalrange F detected in the light intensity detection step is sent to aparameter calculation step.

In the parameter calculation step (S103), the controller 103 calculatesa predetermined light arrival range parameter based on the light arrivalrange F. The light arrival range parameter may be the area S of thelight arrival range F, the volume V of the light arrival range F, or thedistance l from the irradiation position E in light arrival range F tothe outer circumference (outer edge) of the light arrival range F. Thelight arrival range parameter may instead be only the minimum lightarrival distance l2, the light arrival area S and the minimum lightarrival distance l2, the light arrival volume V and the minimum lightarrival distance l2, or the ratio or difference between the maximumlight arrival distance l1 and the minimum light arrival distance l2, orthe combination thereof. The calculated light arrival range parameter issent to a lipid concentration calculation step.

In the lipid concentration calculation step (S104), the controller 103calculates the lipid concentration in the blood based on the lightarrival range parameter. In the lipid concentration calculation step,the lipid concentration may be calculated after the scatteringcoefficient is calculated from the light arrival range parameter.

As described above, the lipid measuring apparatus and method accordingto the present embodiment readily allow noninvasive lipid measurementwith no skill of a measurer by acquiring two-dimensional information onthe light intensity of the light emitted from a living body to acquireinformation on the veins and information on the capillaries.

A lipid measuring apparatus according to another embodiment will next bedescribed. Some portions of the configuration of the lipid measuringapparatus according to the other embodiment are the same as those of theconfiguration of the lipid measuring apparatus according to theembodiment described above, and different portions will therefore beprimarily described.

In the embodiment described above the configuration in which theirradiator 101, the light intensity detector 102, and the controller 103are integrated with one another has been presented by way of example,but not necessarily. The irradiator 101, the light intensity detector102, and the controller 103 may be configured as a system in which theirradiator 101 and the light intensity detector 102 are configured as auser apparatus and the controller 103 is provided in a server apparatusconnected to the user apparatus.

FIG. 7 shows the configuration of a lipid measuring system according tothe embodiment. The system includes a lipid measuring apparatus 200, anaccess point 300, and a user apparatus 400.

The lipid measuring apparatus 200 is an apparatus for calculating lipidconcentration by carrying out a predetermined process based on lightintensity transmitted from the user apparatus 400. The lipid measuringapparatus 200 is specifically a personal computer or a server apparatusas appropriate depending on the number of apparatuses and the amount ofdata to be transmitted and received.

The user apparatus 400 is an apparatus possessed by a user and is astandalone apparatus in some cases or is incorporated in a smartphone, amobile phone, or a wristwatch in other cases. A camera, illumination, acommunication function, and the like provided in a smartphone or amobile phone may be used as an irradiator 401, a light intensitydetector 402, and a communication section 404.

The user apparatus 400 includes the irradiator 401, which radiateslight, the light intensity detector 402, and the communication section404. The communication section 404 transmits the light intensitydetected by the light intensity detector 402. The functions and actionsof the irradiator 401 and the light intensity detector 402 have beendescribed above.

The lipid measuring apparatus 200 includes a communication section 204 aand a controller 203. The communication section 204 receives the lightintensity transmitted from the communication section 404 via the accesspoint 300 and transmits the light intensity to the controller 203.

The configuration of a control system of the lipid measuring apparatus200 will next be described. FIG. 8 is a block diagram of the lipidmeasuring apparatus 200 according to the embodiment. A CPU (centralprocessing unit) 204, a ROM (read only memory) 205, a RAM (random accessmemory) 206, a storage 207, a communication section (external I/F(interface)) 208 are connected to each other via a system bus 209. TheCPU 204, the ROM 205, and the RAM 206 form the controller 203.

The ROM 205 stores in advance a program executed by the CPU 204 andthresholds used by the CPU 204.

The RAM 206 has an area where the program executed by the CPU 204 isdeveloped, a variety of memory areas, such as a work area where theprogram processes data, and other areas.

The storage 207 stores data prepared in advance on appropriate numericalranges of static and dynamic parameters. The storage 207 may be aninternal memory that stores information in a nonvolatile manner, such asan HDD (hard disk drive), a flash memory, and an SSD (solid-statedrive).

The communication section (external I/F) 208 is an interface forcommunication with an external apparatus, for example, a client terminal(PC). The external I/F 208 only needs to be an interface that performsdata communication with an external apparatus and may, for example, bean instrument (such as USB memory) locally connected to the externalapparatus or a network interface for communication via a network. Thefunctions and actions of the controller 203 have been described above.

In the embodiment, the light intensity is transmitted from the userapparatus 400 to the lipid measuring apparatus 200 via the access point300, but not necessarily, and the user apparatus 400 and the lipidmeasuring apparatus 200 may be directly connected to each other via noaccess point, and the user apparatus 400 may transmit the lightintensity over wired communication, wireless communication, or any othermeans.

EXAMPLE

An example of the present invention will be described below, but thepresent invention is not limited to Example described below.

A lipid measuring apparatus according to the present example readilyallows noninvasive lipid measurement with no skill of a measurer byacquiring two-dimensional information on the light intensity of radiatedlight reflected off and scattered by in-blood lipid in a living body andemitted from the living body to acquire information on the veins andinformation on the capillaries.

FIG. 9 shows a result of direct radiation of the light from an LED(irradiator 101) onto the skin of a living body and imaging of the lightarrival range with an infrared light camera (light intensity detector102). FIG. 9 shows that the light radiated from the LED (irradiator 101)diffuses in the living body in the form of concentric circles.

FIG. 10 shows a result of the measurement at the same site of the skinof the living body after lipid loading (after blood turbidityincreases).

In FIG. 10, the light radiated from the LED (irradiator 101) diffuses inthe living body in the form of concentric circles, as in FIG. 9, andcomparison between FIGS. 9 and 10 shows that the amount of spread of thelight toward the periphery decreases in FIG. 10 as compared with FIG. 9.The data shown in FIG. 10 is data on a measured portion where the veinsare invisible in visual inspection.

FIG. 11 shows a result of the measurement in the vicinity of the veinsin the forearm. In the veins, a phenomenon considered as attenuation ofthe light due to the blood is observed, and distorted diffusion insteadof diffusion in the form of concentric circles can be observed.

The thus obtained information allows calculation of the lipidconcentration by using the following approaches:

(1) Approach to calculation of the lipid concentration from the lightarrival area S over which the light diffuses (Approach 1)

(2) Approach to calculation of the lipid concentration from thedistortion of the light arrival range F over which the light diffusesdue to the veins (Approach 2)

(3) Approach to calculation of the lipid concentration from the lightarrival area S over which the light diffuses (Approach 3)

A method for calculating the lipid concentration based on each of theapproaches described above will be described below.

(1) Approach to calculation of the lipid concentration from the lightarrival area S over which the light diffuses (Approach 1)

In this approach, analysis of portions other than the portions above theveins allows the measurement only with information, for example, on thecapillaries, and measurement that does not depend on the measurementsite can be made. In a simplified form, the analysis may be made byusing the light arrival distance in place of the light arrival range orthe light arrival area.

FIG. 12 shows comparison between variation in the lipid concentrationand the light arrival area S in a lipid loading test. FIG. 12A showsgraphs of the amount of temporal change in TG and the temporal change inlight arrival area when lipid is loaded. FIG. 12B shows the correlationbetween the amount of change in TG and the light arrival area. As shownin FIG. 12A, a decrease in the light arrival area S with an increase inthe lipid concentration is observed. The reason for this can be inferredas follows: the distance over which the light diffuses decreases as theamount of scattering due to the lipid particles increases. FIG. 12Bshows that the amount of change in TG and the light arrival area arecorrelated to each other by a degree of correlation of 0.875.

(2) Approach to calculation of the lipid concentration from thedistortion of the light arrival range F over which the light diffusesdue to the veins (Approach 2)

In the case where the measurement is made through the veins, the lightdoes not concentrically diffuse, and the light arrival range F has adistorted shape. In Approach 2, the maximum light arrival distance l1and the minimum light arrival distance l2 between the light incidentpoint and the light arrival point are compared.

FIG. 13 shows the relationship between the minimum light arrivaldistance l2 and the lipid concentration. FIG. 13A shows graphs of showsgraphs of the amount of temporal change in TG and the temporal change inthe minimum light arrival distance l2 when lipid is loaded. FIG. 13Bshows the correlation between the amount of change in TG and the minimumlight arrival distance l2 in FIG. 13A. As shown in FIG. 13A, a decreasein the minimum light arrival distance l2 with an increase in the lipidconcentration is observed. The reason for this can be inferred asfollows: the distance over which the light diffuses decreases as theamount of scattering due to the lipid particles increases. FIG. 13Bshows that the amount of change in TG and the minimum light arrivaldistance l2 are correlated to each other by a degree of correlation of0.877.

(3) Approach to calculation of the lipid concentration from the lightarrival volume V over which the light diffuses (Approach 3)

In this approach, the measurement can be made only with informationparticularly on the capillaries, and measurement that does not depend onthe measurement site can be made.

FIG. 14 shows comparison between variation in the lipid concentrationand the light arrival volume V in a lipid loading test. FIG. 14A showsgraphs of the amount of temporal change in TG and the temporal change inlight arrival area when lipid is loaded. FIG. 14B shows the correlationbetween the amount of change in TG and the light arrival area in FIG.14A. As shown in FIG. 14A, a decrease in the light arrival volume V withan increase in the lipid concentration is observed. The reason for thiscan be inferred as follows: the distance over which the light diffusesdecreases as the amount of scattering due to the lipid particlesincreases. FIG. 14B shows that the amount of change in TG and the lightarrival volume V are correlated to each other by a degree of correlationof 0.851.

Further, the combination of Approaches 1and 2 allows calculation of thelight arrival area S even in a measurement site containing the veins,and information on the veins and capillaries as a whole can be acquired.

In Approach 2, the precision of the measurement as the information onthe veins can be increased by calculating the ratio or differencebetween the maximum light arrival distance l1 and the minimum lightarrival distance l2. Further, in Approach 2, the precision of themeasurement as the information on the veins can be increased bydetermining the ellipticity from the maximum light arrival distance l1and the minimum light arrival distance l2 or by the area of the ellipse.

Further, to increase the accuracy of the information on the veins, thenumber of points at which the light radiated from the irradiator 101 isincident is increased, and the position of the veins can also beidentified by the information from the plurality of points.

FIG. 15 shows the arrangement of the irradiator 101 and the lightintensity detector 102 that differs from the arrangement shown in FIG.2, and FIG. 16 shows an example of the result of imaging based on themethod shown in FIG. 15.

FIG. 16 shows a result of measurement of the blood flow in thecapillaries (at light arrival depth of about 1 mm) by using a laser asthe irradiator 101, irradiating a wide range with the light from thelaser, and measuring speckles produced by the laser light.

The light arrival depth may be adjusted, for example, by adjusting theamount of light from the light source.

FIG. 17 shows a result of the measurement with a subject staying restand having the same attitude in consideration of the influence of thebody temperature, the pulse, and other factors.

FIG. 17A shows graphs of a temporal change in the amount of change in TGand a temporal change in the flow rate when lipid is loaded. FIG. 17Bshows the correlation between the amount of change in TG and the flowrate. As shown in FIG. 17A, a decrease in the flow rate with an increasein the lipid concentration is observed. FIG. 17B shows that the amountof change in TG and the flow rate are correlated to each other by adegree of correlation of 0.757. The above result also shows that thelipid concentration can be calculated from information on the bloodother than the veins.

Comparison of the information on the veins provided by the presentinvention with information on the veins provided, for example, by usinga method described in Reference Literature allows metabolism informationto be obtained more accurately. Comparison between the case where thelight source is in contact with a subject and the case where the lightsource is not in contact with the subject allows information only on theveins to be obtained.

REFERENCE SIGNS LIST

-   100: Lipid measuring apparatus-   101: Irradiator-   102: Light intensity detector-   103: Controller

1. A lipid measuring apparatus comprising: an irradiator that radiateslight having a predetermined light intensity to a predetermined site ofa living body from outside the living body toward inside the livingbody; a light intensity detector that detects a light arrival range inthe living body based on a light intensity of light emitted from theliving body; and a controller that calculates a predetermined lightarrival range parameter based on the light arrival range and calculateslipid concentration in the living body based on the light arrival rangeparameter.
 2. The lipid measuring apparatus according to claim 1,wherein the light arrival range parameter is based on an area of thelight arrival range.
 3. The lipid measuring apparatus according to claim1, wherein the light arrival range parameter is based on a distance fromthe irradiation position in the light arrival range to an outercircumference of the light arrival range.
 4. The lipid measuringapparatus according to claim 1, wherein the light arrival rangeparameter is based on a volume of the light arrival range.
 5. The lipidmeasuring apparatus according to claim 1, wherein the light arrivalrange parameter includes a ratio or a difference between a maximumdistance and a minimum distance from the irradiation position in thelight arrival range to an outer circumference of the light arrivalrange.
 6. The lipid measuring apparatus according to claim 1, whereinthe controller calculates a scattering coefficient from the lightarrival range parameter and then calculates the lipid concentration. 7.A lipid measuring method comprising: an irradiation step of radiatinglight having a predetermined light intensity to a predetermined site ofa living body from outside the living body toward inside the livingbody; a light intensity detection step of detecting a light arrivalrange in the living body based on a light intensity of light emittedfrom the living body; a parameter calculation step of calculating apredetermined light arrival range parameter based on the light arrivalrange; and a lipid concentration calculation step of calculating lipidconcentration in the living body based on the light arrival rangeparameter.
 8. The lipid measuring method according to claim 7, whereinthe light arrival range parameter is based on an area of the lightarrival range.
 9. The lipid measuring method according to claim 7,wherein the light arrival range parameter is based on a distance fromthe irradiation position in the light arrival range to an outercircumference of the light arrival range.
 10. The lipid measuring methodaccording to claim 7, wherein the light arrival range parameter is basedon a volume of the light arrival range.
 11. The lipid measuring methodaccording to claim 7, wherein the light arrival range parameter includesa ratio or a difference between a maximum distance and a minimumdistance from the irradiation position in the light arrival range to anouter circumference of the light arrival range.
 12. The lipid measuringmethod according to claim 7, wherein in the lipid concentrationcalculation step, a scattering coefficient is calculated from the lightarrival range parameter, and the lipid concentration is then calculated.13. A lipid measuring apparatus communicably connected to a userapparatus including an irradiator that radiates light having apredetermined light intensity to a predetermined site of a living bodyfrom outside the living body toward inside the living body, a lightintensity detector that detects a light arrival range in the living bodybased on a light intensity of light emitted from the living body, and acommunication section that transmits the light arrival range detected bythe light intensity detector, wherein the lipid measuring apparatuscomprises a controller that calculates a predetermined light arrivalrange parameter based on the light arrival range transmitted from theuser apparatus and calculates lipid concentration in the living bodybased on the light arrival range parameter.
 14. The lipid measuringapparatus according to claim 13, wherein the light arrival rangeparameter is based on an area of the light arrival range.
 15. The lipidmeasuring apparatus according to claim 13, wherein the light arrivalrange parameter is based on a distance from the irradiation position inthe light arrival range to an outer circumference of the light arrivalrange.
 16. The lipid measuring apparatus according to claim 13, whereinthe light arrival range parameter is based on a volume of the lightarrival range.
 17. The lipid measuring apparatus according to claim 13,wherein the light arrival range parameter includes a ratio or adifference between a maximum distance and a minimum distance from theirradiation position in the light arrival range to an outercircumference of the light arrival range.
 18. The lipid measuringapparatus according to claim 13, wherein the controller calculates ascattering coefficient from the light arrival range parameter and thencalculates the lipid concentration.
 19. The lipid measuring apparatusaccording to claim 2, wherein the light arrival range parameter is basedon a distance from the irradiation position in the light arrival rangeto an outer circumference of the light arrival range.
 20. The lipidmeasuring apparatus according to claim 2, wherein the light arrivalrange parameter is based on a volume of the light arrival range.